In Washington, D.C., in Detroit and in most every major city in America, crowds of thousands participated in the “March For Our Lives” on Saturday, rallying against gun violence.

But if those marches are to have a lasting impact, the movement will need to create an organization that can use its power to apply “regular pressure” and hold politicians accountable, says Michael T. Heaney, University of Michigan organizational studies and political science professor.

“The march was extremely impressive, but it’s not clear yet that it’s sustainable,” Heaney said.

More than 844 sister marches took place on Saturday to mark one-month after17 people were killed and 15 were wounded at Marjory Stoneman Douglas High School in Parkland, Fla.

Heaney attended that main march in Washington and conducted some 290 surveys with participants. Picking marchers at random, Heaney would ask them to fill out a six-page survey, which asked, among other things, about their politics, their past involvement in social movements, their feelings on President Donald Trump and former President Barack Obama and their thoughts on gun control.

While those results have not yet been tabulated, Heaney said he was struck by the “extremely impressive” turnout at the march, which packed the streets of the nation’s capital “shoulder to shoulder” with people.

But if gun control will ever be realized, it will quickly have to transition from a movement to an organization — one that can present the same type of credible threat to politicians that the National Rifle Association does — Heaney said.

“The media loved that young people were speaking and making themselves heard, but is a 12-year-old girl really ready to be the leader of a movement? Or is she just ready to go to middle school?” said Heaney.

Scott Craig, a teacher at Seaholm High School in Birmingham, marched Saturday for his students and his own protection. He said his classes spent four days talking about how they feel.

“They think they’re the generation of mass shootings and that’s not right,” the 63-year-old Southfield resident said. “The security measures we would need would cost a fortune. The only solution is reducing sales of assault weapons.”

For some students, like Aly Johnson and Hassan Bazzi of Churchill High School in Livonia, the movement needs to address more than the availability of guns. Warning signs can’t be ignored either.

“It’s like that PSA commercial Sandy Hook parents made, no one's looking out for the troubled kids that showed warning signs of a planned shooting,” said Johnson, 17.

“We have to watch on social media, make it harder for people to obtain guns and end this epidemic... that’s why we march,” said Bazzi, 18.

U.S. Rep. Brenda Lawrence, D-Southfield, spoke at the Detroit rally in Hart Plaza after she marched alongside students.

“These silent lawmakers, all they want to talk about is the protection of guns,” said Lawrence. “What about the protection of people? This is what we needed and this is sparking change.”

With more than seven months until the November election, whether this change and momentum can continue remains to be seen, said Heaney.

Heaney cited the NRA, which opposes the gun control measures Saturday’s marchers favor, including universal background checks and bans on high-capacity magazines, as an organization that wields money and political power effectively.

“The NRA doesn’t always win” when it targets politicians, but it can make their road back to power tougher than it would have been. The NRA is “not a big protest organization,” Heaney said, but makes its voice heard in other ways.

Representatives for the National Rifle Association did not immediately respond to requests for comment Sunday. On Saturday, the NRA went silent on Twitter as the protests unfolded, in contrast to its reaction to the nationwide school walkouts against gun violence March 14, when it tweeted a photo of an assault rifle and the message “I’ll control my own guns, thank you.”

The group has spoken out on the push to tighten gun laws and called for more security in schools.

Politicians know that when the group speaks, a substantial number of voters will listen, he said.

A movement with gun control as its aim, a movement engaged in a direct battle against the NRA, must become “as fearsome or more fearsome,” he said. And that starts by creating an organization, with chapters at the local level, that can apply pressure to politicians to either pass the laws they want, or risk losing in November.

At the Washington march Saturday, shooting survivor Emma Gonzalez stood silently in front of thousands gathered for 6 minutes and 20 seconds, the time, she said, it took for the shooter to attack.

“The shooter has ceased shooting and will soon abandon his rifle, blend in with the students as they escape and walk free for an hour before arrest,” she told the crowd and thousands watching from elsewhere. “Fight for your lives before it’s someone else’s job.”

Gonzalez is one of several teens from the school to become gun control activists in the wake of the shooting, their efforts galvanizing youth nationwide.

But Gonzalez recognized it is not enough to march, assigning some homework to the demonstrators: “One final plug — Get out there and vote.”

However, Heaney cautioned that simply voting for Democrats would be the equivalent of joining a political party, and would be less effective than opposing specific politicians based on their gun control positions.